In recent years, a fluorescent-lamp-type light emitting diode lamp (hereinafter referred to as “LED lamp”) attachable to an existing illumination device for fluorescent lamps becomes commercially available as an alternative light source to a fluorescent lamp (see, e.g., Japanese Patent Application Publication No. 2004-30929 (JP2004-30929A). The LED lamp (or the LED device) disclosed in JP2004-30929A includes a tubular light-transmitting member and a plurality of light emitting diodes (LEDs) arranged within the light-transmitting member. The light-transmitting member is provided with end caps at its opposite ends. The end caps are mounted to a lamp socket of an illumination device. The LEDs emit light as the electric power is supplied to the LEDs from a lighting unit through the lamp socket.
The method of mounting such a fluorescent-lamp-type LED lamp differs from maker to maker. For example, when one wishes to use the LED lamp in an existing illumination device for fluorescent lamps, the illumination device needs to be remodeled by removing a lighting unit for fluorescent lamps and newly installing a lighting device for LED lamps.
Since the fluorescent lamp and the fluorescent-lamp-type LED lamp look as if they have the same shape, it is likely that a user may confuse the remodeled illumination device with the existing illumination device and may mistakenly mount a fluorescent lamp to the remodeled illumination device. The lighting units for the fluorescent lamp and the LED lamp are designed differently. Therefore, if the fluorescent lamp is mistakenly mounted to the remodeled illumination device, there is a possibility that the fluorescent lamp cannot be turned on and may be adversely affected. In case where a fluorescent-lamp-type LED lamp of different specifications produced by another maker is mistakenly mounted to the remodeled illumination device, there still remains a possibility that the LED lamp cannot be turned on and may be adversely affected as in the case of mounting the fluorescent lamp.
In an effort to prevent erroneous mounting of a lamp, there has been proposed an LED illumination device with specialized end caps (see, e.g., JP2004-30929A).
The LED illumination device disclosed in JP2004-30929A is capable of preventing erroneous mounting of a lamp by using the specialized end caps to eliminate interchangeability with a fluorescent lamp. However, this makes it necessary to replace a lamp socket when the LED lamp is replaced by a fluorescent lamp. In other words, the conventional lamp socket is not usable with both the fluorescent lamp and the LED lamp.